Design and Development Roads Converge at Biocompatibility

Biocompatibility is often treated as a milestone, a box to check on the path to regulatory approval. In reality, it is the cumulative outcome of hundreds of decisions made long before a device ever reaches a test lab. Every choice in materials, manufacturing processes, geometry, packaging, and sterilization shapes the biocompatibility profile of a medical device. When viewed through this lens, biocompatibility is not a test, but a design philosophy. And all roads, no matter where they begin, eventually lead to biocompatibility.

Material Selection: The First Fork in the Road

Material selection is the earliest and most influential determinant of biocompatibility. The chemical composition of a material—whether it’s a base polymer, metal alloy, ceramic, or composite—sets the foundation for the overall device biocompatibility. Ultimately, the material’s chemistry dictates the device’s biological profile. Poor material choices cannot be “tested out” later; they must be designed out from the start.

It is also important to remember that not all suppliers are the same. Where is the competition in that? In practice, each supplier has a proprietary mix for medical-grade polymers that can have significantly different chemical profiles. There is also a varying degree of willingness to disclose more detailed information.

The story, however, doesn’t end with the raw material. Even materials considered “biocompatible” can behave differently depending on additives such as plasticizers, stabilizers, colorants, and processing aids. These substances may migrate, degrade, or interact with sterilization modalities, creating new chemical species that influence biological response. Supplier controls are critical. A seemingly minor change, such as a new stabilizer in a polymer formulation, can alter extractables and leachables profiles. Without a robust change notification process, manufacturers may unknowingly introduce biocompatibility risks.

The final note on materials is with regard to statements of biocompatibility from the supplier: This is a great start to a biocompatible device, but not the final story, especially if there is additional processing (including sterilization) once the material is received.

Manufacturing Processes and Residuals

Manufacturing introduces its own chemical footprint. Molding, machining, curing, and surface treatments can leave behind residual monomers, catalysts, lubricants, or cleaning agents. These residuals often become the primary drivers of cytotoxicity, sensitization, or irritation outcomes.

Packaging: The Often-Overlooked Contributor

Packaging is frequently viewed as a logistics or sterility concern, but it plays a significant role in biocompatibility. Packaging materials and processes can introduce new chemicals or alter the device’s chemistry over time. Films, foils, trays, adhesives, inks, and coatings all have extractables profiles of their own. Under certain conditions, these chemicals can migrate into the device, especially during sterilization or long-term storage. Heat sealing, adhesive curing, and other packaging operations can generate byproducts or stress the device materials. These stresses may accelerate degradation or create new chemical species.

A device’s biocompatibility is not static. Real-time and accelerated aging studies often reveal changes in material chemistry, including oxidation, hydrolysis, or additive migration. Packaging can either mitigate or exacerbate these effects. Beyond preventing contamination, packaging must preserve the chemical integrity of the device throughout its shelf life. When packaging interacts with the device, it becomes part of the biocompatibility equation.

Sterilization Modality: The Final Road with Major Consequences

Sterilization is often the last major step in the manufacturing process, but its impact on biocompatibility can be profound. Each modality interacts differently with materials, sometimes in unexpected ways. Choosing a sterilization method after materials are locked in can lead to costly redesigns. Early alignment between materials and sterilization is essential to avoid biocompatibility failures. Sterilization can create new extractables or degradation products that were not present in the raw material.

Common Sterilization Methods and Their Effects

Each sterilization method offers trade-offs in efficacy, material compatibility, and residual risk.

• Ethylene oxide (EO): Highly effective but leaves behind residual EO, ECH, and other byproducts that must be carefully controlled. Some materials absorb EO and release it slowly, complicating aeration.
• Gamma and e-beam radiation: Can cause polymer chain scission, crosslinking, embrittlement, or discoloration. These changes can alter extractables profiles.
• Steam sterilization: High heat and moisture can degrade polymers, corrode metals, or alter coatings.
• Low-temperature plasma: Generally gentle but can modify surface chemistry in ways that affect biological interactions.

The Interconnected System: How These Roads Converge

Biocompatibility is the sum of all chemical inputs from materials, manufacturing, packaging, and sterilization. No single test can compensate for poor decisions upstream. ISO 10993 testing evaluates the final, sterilized (if applicable) device. If the device contains reactive additives, residual solvents, or sterilization byproducts, those will drive the biological response, regardless of the material’s original classification.

Biocompatibility success depends on early and ongoing collaboration among R&D, quality, regulatory, and manufacturing teams. When these groups work in silos, biocompatibility issues often surface late, when changes are most expensive and difficult to implement.

Designing Your Device with Biocompatibility in Mind

Biocompatibility is not a hurdle to clear at the end of development; it is the destination toward which every design decision leads. Material selection, packaging, and sterilization each leave a chemical fingerprint on the device, shaping its biological safety profile. When design decisions are made intentionally and collaboratively from the beginning, biocompatibility is no longer a challenge but a natural outcome.

Design with biocompatibility in mind from the start, and every road you take will lead you exactly where you need to go.

Audrey Turley has over 25 years of experience working in research, laboratory, and test design functions in the medical device industry. She is a biocompatibility expert, having spent 15 years in the lab performing all the in vitro tests offered at Nelson Labs, which include cytotoxicity, hemolysis (PTT, PT, complement activation, and mechanical hemolysis), and genotoxicity (Ames and chromosome aberration). Turley was responsible for the development of the in vitro mammalian chromosome aberration assay at Nelson Labs. She was also on the team at Nelson Labs that developed and validated the in vitro irritation assay for medical devices. Turley is an active committee member of several working groups with the Association for the Advancement of Medical Instrumentation (AAMI) and on the International Standards Organization (ISO) level as well.

Logan Luke graduated with a degree in microbiology and has five years of experience working at Nelson Labs. He has worked in the Sterilization, IDs, and Packaging departments. He has extensive knowledge in the packaging section, as he has aided many customers with their package testing needs, from the benchtop to troubleshooting and validation design. Luke is well-versed in a broad spectrum of packaging tests, from lot release package testing for pharmaceutical products to full package validations, including shipping and distribution. He is also a member of the PDA.

Robert Dieker has over a decade of experience in the medical device testing industry, with extensive expertise in supporting the biological safety evaluation of medical devices through technical consulting, laboratory coordination, and regulatory risk assessment activities. His expertise includes the development of Biological Evaluation Plans (BEPs) and Reports (BERs), material characterization evaluations, and interpretation of biocompatibility data in accordance with the ISO 10993 series and ISO 14971. Prior to his consulting work, Dieker served as a study director, during which he designed and executed studies related to sterilization validation, dose audits, and routine bioburden testing. His hands-on laboratory background strengthens his ability to provide practical testing strategies, develop clear technical documentation, and support regulatory submissions for global markets, including FDA and MDR. Dieker also contributes to industry initiatives through standards working groups, cross-functional collaboration, and internal training and mentorship activities.